The present invention relates to methods and circuits for synchronising optical signals, and to optical switches incorporating such circuits.
Synchronisation is an important issue in the design of high-speed optical switches for use in optical telecommunications, both in the context of a synchronous self-routing packet systems, and in synchronous OTDM systems. The use of a non-linear optical loop mirror (NOLM) incorporating an optical semiconductor positioned asymmetrically in the loop for demultiplexing a signal at bit rates as high as a TeraHertz has been demonstrated ["A TeraHertz optical asymmetric demultiplexer", Sokoloff et al, IEEE Photonics Technology Letters, 5 (1993) pp 787-790]. However, for effective functioning of such a switch, it is essential that synchronisation is maintained between the gating or control signal and the datastream which is to be switched. In practice, synchronisation can easily be lost, for example, because of thermal effects in the optical system.